This invention relates generally to three-phase load centers and more particularly to a three-phase extruded base pan configuration for such a load center.
One-piece base pan configurations extruded from thermally conductive and electrically insulative material have come into being because they are simple to manufacture, easy to use, minimize parts and reduce expenses associated with the manufacture of load centers. One advantage of an extruded base pan configuration is that is offers the potential for saving space. Space is important in many residential and light industrial applications where there is only the thickness of a wall stud within which to place a load center. Obviously, the thinner the load center is, the more desirable it is for use in these limited space environments. The base pan itself can be a limiting factor where space is a requirement, because some base pans, for example those constructed of metal components, require many parts which are held together with bolts or screws making them bulky. In addition to being bulky on their own, the metal base pans require insulators to insulate the metal conductive base pan components from the live bus bars. This further adds to the weight, complexity and size of the load center. It will be appreciated that it would be highly desirable to have a base pan constructed of insulative material which can be extruded in a simple, compact fashion to minimize the dimensions of the load center.
As the physical dimensions of load centers decrease, heat dissipation becomes a problem because the load center must meet certain operating conditions which restrict the temperature of the bus bars under load. In the old-fashioned metal base pan load centers, the components were spaced apart so that there was adequate ventilation, or the bus bars were made with sufficient cross-sectional area that the temperature rise in them was not a serious problem. However, when one goes to extruded insulative base pans to save space, then the size of the bus bars proportionately shrinks to maintain the neat, compact appearance. With the shrinking of the bus bars, heat dissipation becomes a problem. Accordingly, it will be appreciated that it would be highly desirable to have an extruded base pan which utilizes small cross-sectional area bus bars but provides adequate cooling so that the temperature rise in the bus bars is not excessive.
Accordingly, it is an object of the present invention to provide an extruded bas pan formed of electrically insulative material.
Another object of the invention is to provide an extruded base pan which provides adequate ventilation to maintain a low operating temperature for the bus bars.